General: The lighting has brought the woodgrain out nicely.
Composition: Placing the knot in the upper 1/3 of the image adds interest however the even number of nails, though balanced, don't seem to work with it. Odd numbers usually work better. That's not to say never use even numbers just that in this composition an odd number of nails may have worked better.
Exposure: Even though the lighting has brought out the grain in the wood, the nails are overly bright. It was probably difficult to balance the exposure of the nails and the wood. A different time of day or a slightly shaded spot may have helped with this balance.
Impact: This is very subjective. The colour and grain of the wood does provide some however the image as a whole does not. A different composition and/or lighting may have helped here.